Image processing device and non-transitory recording medium including setting of a prohibition period that prohibits reception of a different synchronization signal

ABSTRACT

An image processing device includes a reception unit and a setting unit. The reception unit receives an input image signal, and a synchronization signal used to generate an output image signal on a basis of the input image signal. The setting unit sets, after the reception unit receives the synchronization signal, a reception prohibition period that prohibits reception of a different synchronization signal by the reception unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 USC 119 fromJapanese Patent Application No. 2017-093619 filed May 10, 2017.

BACKGROUND Technical Field

The present invention relates to an image processing device and anon-transitory recording medium.

SUMMARY

According to an aspect of the invention, there is provided an imageprocessing device including a reception unit that receives an inputimage signal, and a synchronization signal used to generate an outputimage signal on a basis of the input image signal, and a setting unitthat sets, after the reception unit receives the synchronization signal,a reception prohibition period that prohibits reception of a differentsynchronization signal by the reception unit.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention will be described indetail based on the following figures, wherein:

FIG. 1 is a block diagram illustrating an image processing systemaccording to a first exemplary embodiment of the present invention;

FIG. 2 is a diagram illustrating an example of a signal conforming tothe LVDS standard;

FIG. 3 is a block diagram illustrating an image processing circuitaccording to the first exemplary embodiment;

FIG. 4 is a block diagram illustrating a noise cancellation circuitaccording to the first exemplary embodiment;

FIG. 5 is a block diagram illustrating a noise cancellation circuitaccording to the second exemplary embodiment;

FIG. 6 is a diagram illustrating a timing chart;

FIG. 7 is a block diagram illustrating a noise cancellation circuitaccording to the third exemplary embodiment;

FIG. 8 is a block diagram illustrating a noise cancellation circuitaccording to the fourth exemplary embodiment;

FIG. 9 is a diagram illustrating a timing chart;

FIG. 10 is a diagram illustrating a timing chart; and

FIG. 11 is a diagram illustrating a timing chart.

DETAILED DESCRIPTION First Exemplary Embodiment

FIG. 1 illustrates an example of an image processing system according toa first exemplary embodiment. As an example, the image processing systemincludes an image reading device 10 provided with a function of readingan image, a controller board 12 provided with a function of processingan image, and a cable 14. An image signal generated due to image readingby the image processing device 10 is sent to the controller board 12through the cable 14.

The image reading device 10 includes a sensor 16 and an analog front-end(AFE) 18.

The sensor 16 is made up of a CCD or CIS, for example, and is providedwith a function of reading an image. Obviously, a different imagereading sensor may also be used as the sensor 16. A base clock signal(CLK) conforming to a predetermined frequency is sent from the AFE 18 tothe sensor 16, and the sensor 16 conducts image reading insynchronization with the base clock signal (CLK). With this arrangement,an image signal is generated as an analog signal, in synchronizationwith the base clock signal (CLK). The image signal is sent from thesensor 16 to the AFE 18.

For the image reading method, a line-sequential method is adopted, forexample. With a line-sequential method, the sensor 16 includes a linesensor, turns on red (R) light (linear light), green (G) light (linearlight), and blue (B) light (linear light) sequentially in accordancewith a predetermined image reading cycle (where the length of one cyclecorresponds to the length of one CLK), and uses the line sensor to readan image for each of the colors R, G, and B. By following the readingsequence and cycle, an R-line image signal, a G-line image signal, and aB-line image signal are generated sequentially. For example, each imagesignal is generated every one CLK. By causing the sensor 16 to read animage while moving the sensor 16 in a main scanning direction (adirection that crosses (for example, a direction orthogonal to) thedirection in which the line sensors extend), an image is read in unitsof lines, with image signals of different colors (the R-line imagesignal, G-line image signal, and B-line image signal) being generatedfor every line.

As a method other than the line-sequential method, a point-sequentialmethod may also be adopted. With a point-sequential method, the sensor16 turns on R light (point light), G light (point light), and B light(point light) sequentially in accordance with a predetermined imagereading cycle (where the length of one cycle corresponds to the lengthof one CLK), and reads an image for each of the colors R, G, and B. Byfollowing the reading sequence and cycle, an R image signal, a G imagesignal, and a B image signal are generated sequentially. For example,each image signal is generated every one CLK. By causing the sensor 16to read an image while moving the sensor 16, an image is read in unitsof pixels, with the R image signal, G image signal, and B image signal)being generated for every pixel. For example, by causing the sensor 16to read an image while moving the sensor 16 in a sub scanning direction,and additionally causing the sensor 16 to move in a main scanningdirection (for example, a direction orthogonal to the sub scanningdirection), an image of each pixel is read.

The AFE 18 is provided with a function of receiving the image signalfrom the sensor 16 as an analog signal, and by applying processing suchas offset adjustment and amplification to the image signal, generatingan image signal as a digital signal.

Also, the AFE 18 synchronizes with the base clock signal (CLK), andgenerates a synchronization signal indicating the reading start time ofeach image. With this arrangement, the synchronization signal isgenerated every one CLK. In the case in which a line-sequential methodis adopted, the AFE 18 generates a synchronization signal indicating thereading start time of the image of each line. For example, the AFE 18generates a synchronization signal corresponding to the R-line imagesignal (a signal indicating the reading start time of the R-line imagesignal), a synchronization signal corresponding to the G-line imagesignal (a signal indicating the reading start time of the G-line imagesignal), and a synchronization signal corresponding to the B-line imagesignal (a signal indicating the reading start time of the B-line imagesignal). In the case in which a point-sequential method is adopted, theAFE 18 generates a synchronization signal indicating the reading starttime of the image of each pixel. The image signal and synchronizationsignal of each color as well as the base clock signal (CLK) are sentfrom the image reading device 10 to the controller board 12 through thecable 14. Hereinafter, the image generated by the AFE 18 as a digitalsignal will be designated the “input image signal”.

In the following, as an example, suppose that an image has been read bya line-sequential method. In this case, a horizontal synchronizingsignal (HSYNC) is used as the line synchronization signal, for example.When generating an output image signal on the basis of the input imagesignal of each line (for, example, when drawing an image using the inputimage signal), this synchronization signal (HSYNC) is utilized to alignthe image of each line with respect to the main scanning direction.

The controller board 12 includes an image processing circuit 20 as anexample of an image processing device. The image processing circuit 20is provided with a function of receiving an input image signal as adigital signal sent from the image reading device 10, and applying imageprocessing to the input image signal. For example, the image processingcircuit 20 receives an input image signal and correspondingsynchronization signal for each color, as well as the base clock signal(CLK), and by utilizing the synchronization signals, combines the R-lineinput image signal, the G-line input image signal, and the B-line inputimage signal to thereby generate an output image signal.

The output image signal is output to a printer, for example, which is anexample of an image output device. In the printer, printing may beperformed in accordance with the output image signal. As anotherexample, the output image signal may be output to a display device, andin the display device, an image may be displayed in accordance with theoutput image signal. An image processing system according to the presentexemplary embodiment may be built into a printer, or may be built into adisplay device or the like.

In the first exemplary embodiment, a transmission method conforming tothe low-voltage differential signaling (LVDS) standard is used as theimage transmission method. FIG. 2 illustrates an example of a signalconforming to the LVDS standard (hereinafter designated an “LVDSsignal”). An LVDS signal is made up of a 5-bit signal and a 30-bit inputimage signal. In the 5-bit signal, there is embedded a signal such as asignal indicating “H”, a signal indicating “L”, or a signal toggled at apredetermined timing like a synchronization signal. In the firstexemplary embodiment, as described later, a signal of several of the 5bits is used as the synchronization signal described above. Note thatalthough the LVDS standard is used, a standard that may include a signalof multiple bits other than the input image signal may also be used,even if a standard other than the LVDS standard.

Hereinafter, the image processing circuit 20 will be described in detailwith reference to FIG. 3. FIG. 3 is a block diagram illustrating theimage processing circuit 20. The image processing circuit 20 includes anLVDS receiver 22, a noise cancellation circuit 24, an image writingcircuit 26, memory 28, and an image reading circuit 30.

The LVDS receiver 22 is provided with a function of receiving an LVDSsignal (a 5-bit signal and a 30-bit input image signal) sent from theAFE 18 of the image reading device 10 through the cable 14, convertingthe differential signals into a single signal, and extracting the 30-bitinput image signal (DATA) and the 5-bit signal (Signal). The 30-bitinput image signal and the 5-bit signal are output to the noisecancellation circuit 24 downstream. Also, the LVDS receiver 22 receivesthe base clock signal (DCLK) sent from the AFE 18, and outputs the baseclock signal (CLK) to the noise cancellation circuit 24.

The noise cancellation circuit 24 is provided with a function ofreceiving the 30-bit input image signal and the 5-bit signal, and byremoving the effects of noise, outputting a noise-canceled input imagesignal and synchronization signal. The noise is electrical noise such aselectrostatic noise, for example, and is superimposed onto the signalduring transmission. The processing by the noise cancellation circuit 24will be described in detail later. Also, the base clock signal (CLK) isoutput from the noise cancellation circuit 24 to the image writingcircuit 26.

The image writing circuit 26 is provided with a function of receivingthe input image signal, the synchronization signal, and the base clocksignal (CLK) output from the noise cancellation circuit 24, and writing(storing) the input image signal in the memory 28. Specifically, theimage writing circuit 26 utilizes the synchronization to write theR-line input image signal in R-memory, write the G-line input imagesignal in G-memory, and write the B-line input image signal in B-memoryin the memory 28.

The image reading circuit 30 is provided with a function of reading outthe input image signal written (stored) in the memory 28 as an outputimage signal, and outputting the output image signal. Specifically, theimage reading circuit 30 reads out the R-line input image signal fromthe R-memory, reads out the G-line input image signal from the G-memory,and reads out the B-line input image signal from the B-memory, combineseach of the input image signals to generate an output image signal, andoutputs that output image signal. The image reading circuit 30 generatesand output an output image signal for each line by reading out each ofthe input image signals for each line. The output image signal may beoutput to a printer, for example, and printing may be performed inaccordance with the output image signal in the printer, or the outputimage signal may be output to a display device, and an image may bedisplayed in accordance with the output image signal in the displaydevice.

Hereinafter, the noise cancellation circuit 24 will be described indetail with reference to FIG. 4. FIG. 4 is a block diagram illustratinga noise cancellation circuit 24 according to the first exemplaryembodiment. The noise cancellation circuit 24 includes a reception unit32, a recognition unit 34, and an output unit 36.

The reception unit 32 is provided with a function of receiving the30-bit input image signal, the synchronization signal for each color,and the base clock signal (CLK) sent from the LVDS receiver 22. Asdescribed above, the sensor 16 reads an image in accordance with apredetermined image reading cycle (a cycle corresponding to the lengthof one CLK), and the input image signal, synchronization signal, andbase clock signal (CLK) are sent periodically from the image readingdevice 10 to the controller board 12. The reception unit 32 receives theinput image signal, synchronization signal, and base clock signal (CLK)sent periodically in this way.

The recognition unit 34 is provided with a function of recognizing agenuine synchronization signal used to generate the output image signalon the basis of the input image signal.

The output unit 36 is provided with a function of outputting the inputimage signal and the synchronization signal received by the receptionunit 32 to the image writing circuit 26 downstream.

Hereinafter, the processing by the recognition unit 34 will be describedin detail.

In the first exemplary embodiment, a synchronization signal having asignal pattern is used as the synchronization signal. Also, thesynchronization signal for each color has a different signal pattern.Such synchronization signals are expressed using the 5-bit signal above.For example, information from 4 bits out of the 5 bits is utilized togenerate a different synchronization signal for each color.Specifically, the synchronization signal for R is expressed by “0101” (aprescribed pattern for R), the G synchronization signal is expressed by“1010” (a prescribed pattern for G), and the synchronization signal forB is expressed by “1001” (a prescribed pattern for B). Thesesynchronization signals are generated by the AFE 18.

The recognition unit 34 receives a synchronization signal having one ofthe above signal patterns, and on the basis of the signal pattern,identifies the color expressed by the input image signal correspondingto the synchronization signal (that is, the color corresponding to thesynchronization signal).

Specifically, in the case in which the signal pattern of the receivedsynchronization signal corresponds to the prescribed pattern for R (forexample, in the case in which the signal pattern matches the prescribedpattern for R), the recognition unit 34 identifies the colorcorresponding to that synchronization signal as “R (red)”, andrecognizes that synchronization signal as a genuine synchronizationsignal for R. Similarly, in the case in which the signal patterncorresponds to the prescribed pattern for G (for example, in the case inwhich the signal pattern matches the prescribed pattern for G), therecognition unit 34 identifies the color corresponding to thatsynchronization signal as “G (green)”, and recognizes thatsynchronization signal as a genuine synchronization signal for G.Similarly, in the case in which the signal pattern corresponds to theprescribed pattern for B (for example, in the case in which the signalpattern matches the prescribed pattern for B), the recognition unit 34identifies the color corresponding to that synchronization signal as “B(blue)”, and recognizes that synchronization signal as a genuinesynchronization signal for B.

The output unit 36 outputs the synchronization signal recognized as agenuine synchronization signal by the recognition unit 34, and the inputimage signal corresponding to the synchronization signal, to the imagewriting circuit 26 downstream.

The image writing circuit 26 receives the input image signal andsynchronization signal (genuine synchronization signal) output from theoutput unit 36, and writes the input image signal in the memory 28. Asabove, since the color corresponding to each synchronization signal isidentified on the basis of a signal pattern included in thesynchronization signal, the image writing circuit 26 may utilize theidentification result to write the R-line input image signal in theR-memory, write the G-line input image signal in the G-memory, and writethe B-line input image signal in the B-memory. The image reading circuit30 reads out the input image signal for each color written in this wayfrom the memory 28 for each line, and combines the input image signalsfor the respective colors on every line to generate and output an outputimage signal. With this arrangement, an output image signal for eachline is generated.

On the other hand, in the case in which the signal pattern of thesynchronization signal received by the reception unit 32 does notcorrespond to any of the prescribed pattern for R, the prescribedpattern for G, or the prescribed pattern for B, the recognition unit 34does not recognize that synchronization signal as a genuinesynchronization signal (for example, the recognition unit 34 recognizesthat synchronization signal as a non-genuine synchronization signal). Inthis case, the output unit 36 does not output the synchronization signalnot recognized as a genuine synchronization signal, or the input imagesignal corresponding to the synchronization signal, to the image writingcircuit 26. The image writing circuit 26 writes input image signalscorresponding to genuine synchronization signals in the memory 28, andthe image reading circuit 30 reads out input image signals written inthe memory 28 to generate and output an output image signal. In thisway, an output image signal is generated without using an input imagesignal corresponding to a synchronization signal not recognized as agenuine synchronization signal.

As above, according to the first exemplary embodiment, a synchronizationsignal is made up of a multi-bit signal pattern, and the synchronizationsignal is identified by the signal pattern. For this reason, even in thecase in which noise is superimposed onto the synchronization signal, theinput or non-input of the synchronization signal is recognized moreaccurately compared to the case in which the synchronization signal ismade up of a 1-bit signal, and the occurrence of image misalignment(image shift) or misregistration (misalignment of the respective colorcomponents of an image) caused by misrecognition of the synchronizationsignal is reduced. Also, since the color indicated by thesynchronization signal is identified more accurately compared to thecase in which the synchronization signal is made up of a 1-bit signal,the color expressed by the input image signal corresponding to thesynchronization signal is identified more accurately.

At this point, consider a case in which noise is superimposed onto asynchronization signal (for example, the synchronization signal for B)for a certain line (for example, the 1st line), and the synchronizationsignal is not input into the image processing circuit 20. For example,suppose that respective images are read in order of R line, G line, Bline. In this case, the first synchronization signal corresponds to theR-line input image signal, the second synchronization signal correspondsto the G-line input image signal, and the third synchronization signalcorresponds to the B-line input image signal. Thereafter,synchronization signals and input image signals are generated and outputin that order.

First, processing according to a comparative example will be described.In the comparative example, suppose that the synchronization signal ismade up of a 1-bit signal (for example, a signal indicating “H” or “L”),and suppose that the input or non-input of the synchronization signal isrecognized by “H” and “L”. In the case in which noise is superimposedonto the synchronization signal for B on the first line, and thatsynchronization signal is not input into the image processing circuit,the synchronization signal input next after the synchronization signalfor B (the next synchronization signal being the synchronization signalfor R on the next line, namely, the second line) is recognized as thesynchronization signal for B on the first line. In that case, the R-lineinput image signal for the first line, the G-line input image signal forthe first line, and the R-line input image signal for the second lineare recognized as the input image signals for the first line, and anoutput image signal is generated on the basis of these input imagesignals. The R-line input image signal for the second line is a signalexpected to be output or drawn as the second line, but in the abovecase, becomes output or drawn as the first line. In other words, theposition of the R-line input image for the second line is shifted(described more specifically, the position (drawing position) of theR-line input image is shifted to the position of the first line in themain scanning direction), thereby causing the color to be reproduced tobecome shifted from the original color. On the second and subsequentlines, image misalignment and misregistration occur similarly. In thisway, in the comparative example, in the case in which noise issuperimposed onto the synchronization signal for a certain line, andthat synchronization signal is not input into the image processingcircuit, image misalignment and misregistration occur on that line andother lines.

In the first exemplary embodiment, the synchronization signal for eachcolor is identified on the basis of a signal pattern, and thus in thecase in which the synchronization signal for B on the first line is notinput, the recognition unit 34 recognizes that the synchronizationsignal for B on the first line has not been received by the receptionunit 32. In this case, in the case in which the synchronization signalfor R and the synchronization signal for G on the first line have beenrecognized as genuine synchronization signals, the image writing circuit26 writes the R-line input image signal and the G-line input imagesignal for the first line in the memory 28, and the image readingcircuit 30 reads out and combines the R-line input image signal and theG-line input image signal from the memory 28 to generate and output anoutput image signal. For the next line, namely, the second line, in thecase in which the synchronization signal for R, the synchronizationsignal for G, and the synchronization signal for B are recognized asgenuine synchronization signals, the R-line input image signal, theG-line input image signal, and the B-line input image signal for thesecond line are written in the memory 28, and these input image signalsare read out to generate an output image signal. In this way, for thesecond line, an output image signal is generated on the basis of theinput image signals for the second line, and thus the image of thesecond line is generated correctly. The third and subsequent lines arealso similar. In this way, even in the case in which noise issuperimposed onto a synchronization signal, the target affected by suchnoise is the image of the line corresponding to the synchronizationsignal affected by the noise, whereas the images of the subsequent linesare not affected by the noise. As a result, the occurrence of imagemisalignment and misregistration is reduced compared to the comparativeexample above.

Also, according to the first exemplary embodiment, since the colorindicated by the synchronization signal is identified, processing likethe following may also be conducted. For example, when the receptionunit 32 receives three synchronization signals in succession, in thecase in which multiple synchronization signals for the same color areincluded among those three synchronization signals, the synchronizationsignal received earlier by the reception unit 32 among the multiplesynchronization signals is identified as being a synchronization signalfor a different line than the synchronization signal received later. Forexample, in the case of being unaffected by noise or the like, thereception unit 32 receives a synchronization signal for R, asynchronization signal for G, and a synchronization signal for B insuccession. For this reason, multiple synchronization signals for thesame color are not included among these three synchronization signals.On the other hand, in the case in which the reception unit 32 receives asynchronization signal for R, a synchronization signal for G, and asynchronization signal for R in succession due to the effects of noiseor the like, the earlier synchronization signal for R and the latersynchronization signal for R are identified as being synchronizationsignals for different lines. Since such identification is possible, thelater synchronization signal for R is kept from being misrecognized as asynchronization signal for the previous line.

The above example deals with a color image, but may also deal with amonochrome image. A monochrome image may be an image expressed with thetwo tones of white and black, or an image expressed by grayscale (forexample, an image expressed by 256 tones). Even in the case of dealingwith a monochrome image, the synchronization signal has a predeterminedsignal pattern, and a synchronization signal having the signal patternis recognized as a genuine synchronization signal. By reading an imageon each line, an input image signal (monochrome image signal) for eachline is generated, and by using the synchronization signal to draw theinput image signal for each line in the main scanning direction, anoutput image signal is generated. Even in the case in which noise issuperimposed onto the synchronization signal, and the synchronizationsignal is not input into the image processing circuit 20, according tothe first exemplary embodiment, the occurrence of image misalignment oneach line (image misalignment in the main scanning direction) is reducedcompared to the comparative example.

Note that although a line-sequential method is used in the aboveexample, a point-sequential method may also be used. Even in this case,the synchronization signal corresponding to the input image signal isrecognized on the basis of a signal pattern. With this arrangement, inthe case in which a color image is generated, the occurrence of imagemisalignment and misregistration is reduced compared to the comparativeexample, while in the case in which a monochrome image is generated, theoccurrence of image misalignment is reduced compared to the comparativeexample.

Second Exemplary Embodiment

Hereinafter, an image processing system according to the secondexemplary embodiment will be described with reference to FIGS. 5 and 6.FIG. 5 is a block diagram illustrating a noise cancellation circuit 24Aaccording to the second exemplary embodiment. FIG. 6 is a diagramillustrating a timing chart.

The image processing system according to the second exemplary embodimentincludes the noise cancellation circuit 24A illustrated in FIG. 5instead of the noise cancellation circuit 24 according to the firstexemplary embodiment. The configuration other than the noisecancellation circuit 24A is the same as the configuration according tothe first exemplary embodiment. Hereinafter, the noise cancellationcircuit 24A will be described.

The noise cancellation circuit 24A includes a reception unit 32, a masksetting unit 38, and an output unit 36.

Since the reception unit 32 and the output unit 36 are provided with thesame functions as in the first exemplary embodiment, description thereofwill be reduced or omitted.

The mask setting unit 38 is provided with a function of setting a maskperiod that prohibits the reception of a synchronization signal from thereception unit 32 after the reception unit 32 receives a synchronizationsignal (corresponding to an example of a reception prohibition period).For example, the mask setting unit 38 sets a mask period for each color.In the second exemplary embodiment, the length of the mask period is thesame for each color. For example, the time at which the reception unit32 receives a synchronization signal is set as the start point of themask period. Also, the length of the mask period is less than the lengthof the base clock signal (the length of one CLK), for example. Describedin further detail, the length of the mask period is determined on thebasis of the length of the 1-line image reading time by the sensor 16(the length of time taken to read an image of one color line), and isless than the length of the image reading time, for example. In otherwords, the mask period is set spanning from the time at which thereception unit 32 receives a synchronization signal (start point) untila time before the time at which the reception unit 32 is predicted toreceive the next synchronization signal (end point).

Since the sensor 16 conducts image reading in a predetermined colororder in accordance with a predetermined image reading cycle (in whichthe length of one cycle corresponds to the length of one CLK), thetiming at which the input image signal and the synchronization signalfor each color are received by the reception unit 32 is predetermined,and that timing is predicted. Described in further detail, when theinitial synchronization signal (for example, the synchronization signalfor R on the first line) is received by the reception unit 32, the timeof that reception is treated as a start point, and the timings of thereception of subsequent synchronization signals by the reception unit 32are predicted. Since the image reading by the sensor 16 is conductedevery one CLK, a synchronization signal is predicted to be received bythe reception unit 32 every one CLK. The mask setting unit 38 sets amask period having a fixed length in accordance with the image readingcycle. In other words, the mask setting unit 38 sets a mask periodhaving a fixed length every one CLK. Note that the reception unit 32still receives the input image signal even during the mask period.

Hereinafter, processing by the mask setting unit 38 will be described indetail with reference to FIG. 6. FIG. 6 illustrates an example of inputimage signals and synchronization signals input into the noisecancellation circuit 24A, and input image signals and synchronizationsignals output from the noise cancellation circuit 24A.

The input data 40R1, 40G1, and 40B1 represent the input image signalsfor the first line. The input data 40R1 represents the R-line inputimage signal, the input 40G1 represents the G-line input image signal,and the input data 40B1 represents the B-line input image signal.

Similarly, the input data 40R2, 40G2, and 40B2 represent the input imagesignals for the second line. The input data 40R2 represents the R-lineinput image signal, the input 40G2 represents the G-line input imagesignal, and the input data 40B2 represents the B-line input imagesignal.

Also, the synchronization signals 42R1, 42G1, and 42B1 (input BOS)represent the synchronization signals for the first line. Thesynchronization signal 42R1 is the synchronization signal correspondingto the input data 40R1, the synchronization signal 42G1 is thesynchronization signal corresponding to the input data 40G1, and thesynchronization signal 42B1 is the synchronization signal correspondingto the input data 40B1.

Similarly, the synchronization signals 42R2, 42G2, and 42B2 (input BOS)represent the synchronization signals for the second line. Thesynchronization signal 42R2 is the synchronization signal correspondingto the input data 40R2, the synchronization signal 42G2 is thesynchronization signal corresponding to the input data 40G2, and thesynchronization signal 42B2 is the synchronization signal correspondingto the input data 40B2.

The reception unit 32 receives input data as an input image signal, asynchronization signal, and the base clock signal (CLK). Every one CLK,an image of each color is read in the order of R line, G line, B line,input data (an input image signal) for each color and a correspondingsynchronization signal are generated, and the input data for each color,the synchronization signal, and the base clock signal (CLK) are inputinto the reception unit 32. In the case of being unaffected by noise orthe like, the reception unit 32 receives input data, a synchronizationsignal, and the base clock signal (CLK) every one CLK.

In the case in which the reception unit 32 receives a synchronizationsignal, after the reception of the synchronization signal, the masksetting unit 38 treats the reception as a start point, and sets a maskperiod that acts as a reception prohibition period. The mask settingunit 38 sets a mask period for each color. The reception unit 32 doesnot receive a synchronization signal during the mask period, and insteadreceives a synchronization signal during the time after the mask periodelapses but before the next mask period is set.

For example, in the case in which the reception unit 32 receives thesynchronization signal 42R1 for R, the mask setting unit 38 treats thetime of the reception of the synchronization signal 42R1 as the startpoint, and sets a mask period 44R1 having a predetermined length oftime. The length of the mask period 44R1 is less than the length of theimage reading time taken to generate the next input image signal, namelythe input data 40G1 (less than the length of the image reading time forone G line by the sensor 16). Consequently, the mask period 44R1 is setspanning from the time at which the reception unit 32 receives thesynchronization signal 42R1 (start point) until the time before the timeat which the reception unit 32 is predicted to receive the nextsynchronization signal 42G1 (end point). The reception unit 32 does notreceive a synchronization signal during the mask period 44R1, andinstead receives the next synchronization signal during the time afterthe mask period 44R1 elapses but before the next mask period 44G1 isset. By fixing the length of the mask period as above, a mask period isset until the image reading for each color is completed, and during thatperiod, the reception of a synchronization signal by the reception unit32 is prohibited. Since a mask period is not set in the period whenimage reading is predicted to be completed and the next synchronizationsignal is predicted to be input into the reception unit 32, during thatperiod, a synchronization signal is received by the reception unit 32.

After the mask period 44R1 elapses, and the reception unit 32 receivesthe next synchronization signal 42G1, the mask setting unit 38 treatsthe time of the reception of the synchronization signal 42G1 as thestart point, and sets the mask period 44G1. Thereafter, the flow issimilar, and the mask setting unit 38 sets a mask period in accordancewith the reception of a synchronization signal by the reception unit 32.With this arrangement, the reception unit 32 repeatedly receives thesynchronization signal for R, the synchronization signal for G, and thesynchronization signal for B in order.

In FIG. 6, the synchronization signal 46R1 (s_lso) is a signalcorresponding to the synchronization signal 42R1 received by thereception unit 32 (for example, the same signal as the synchronizationsignal 42R1), while the synchronization signal 46G1 (s_lso) is a signalcorresponding to the synchronization signal 42G1 received by thereception unit 32 (for example, the same signal as the synchronizationsignal 42G1). This applies similarly to the other synchronizationsignals.

The synchronization signal 48R1 (s_lsor) is a signal corresponding tothe synchronization signal 46R1 (s_lso), while the synchronizationsignal 48R2 (s_lsor) is a signal corresponding to the synchronizationsignal 46R2 (s_lso). The synchronization signals 48R1, 48R2, and so onrepresent the synchronization signals for R.

The output data 50R1 is the same signal as the input data 40R1 receivedby the reception unit 32, and the output data 50G1 is the same data asthe input data 40G1 received by the reception unit 32. This appliessimilarly to the other output data. The output data is input imagesignals output by the output unit 36 to the image writing circuit 26downstream.

The synchronization signal 52R1 (output RLSO_RGB) is a signalcorresponding to the synchronization signal 46R1 (s_lso), while thesynchronization signal 52G1 (output RLSO_RGB) is a signal correspondingto the synchronization signal 46G1 (s_lso). This applies similarly tothe other synchronization signals. The synchronization signals 52R1,52G1, and so on are synchronization signals output by the output unit 36to the image writing circuit 26 downstream.

The synchronization signal 54R1 (output RLSO_R) is a signalcorresponding to the synchronization signal 52R1 (output RLSO_RGB),while the synchronization signal 54R2 (output RLSO_R) is a signalcorresponding to the synchronization signal 52R2 (output RLSO_RGB). Thesynchronization signals 54R1, 54R2, and so on represent thesynchronization signals for R. The synchronization signals 54R1, 54R2,and so on are synchronization signals output by the output unit 36 tothe image writing circuit 26 downstream.

The synchronization signal 54R1 (output RLSO_R) is output to the imagewriting circuit 26 at the same timing as the synchronization signal 52R1(output RLSO_RGB), while the synchronization signal 54R2 (output RLSO_R)is output to the image writing circuit 26 at the same timing as thesynchronization signal 52R2 (output RLSO_RGB). This applies similarly tothe other synchronization signals. By this configuration, the imagewriting circuit 26 recognizes the synchronization signal 52R1 (outputRLSO_RGB) input at the same timing as the synchronization signal 54R1(output RLSO_R) as a synchronization signal for R, recognizes thesynchronization signal 52G1 (output RLSO_RGB) input next as asynchronization signal for G, and recognizes the synchronization signal52B1 (output RLSO_RGB) input next as a synchronization signal for B. Theimage writing circuit 26 recognizes the synchronization signals 52R1,52G1, and 52B1 as synchronization signals for the same line, recognizesthe output data 50R1, 50G1, and 50G1 input together with thesesynchronization signals as input image signals for the same line, andwrites the output data 50R1, 50G1, and 50B1 (input image signals) in thememory 28. When the next synchronization signal 52R2 (output RLSO_RGB)and the synchronization signal 54R2 (output RLSO_R) are input into theimage writing circuit 26, the image writing circuit 26 recognizes thesynchronization signal 52R2 (output RLSO_RGB) as a synchronizationsignal for R on the next line, and writes the output data (input imagesignal) in the memory 28, similarly to the above. Thereafter, theprocess is similar.

Note that even in the first exemplary embodiment, the synchronizationsignals (s_lso), (s_lsor), (RLSO_RGB), and (RLSO_R) may be generated,the synchronization signals (RLSO_RGB) and (RLSO_R) may be output to theimage writing circuit 26 together with output data, and the imagewriting circuit 26 may write the output data in the memory 28 inaccordance with the synchronization signals.

According to the second exemplary embodiment, since a synchronizationsignal is not received during the mask period, a synchronization signalwith superimposed noise, for example, is kept from being received by thereception unit 32. With this arrangement, compared to the case of notsetting a mask period, the occurrence of image misalignment andmisregistration caused by noise is reduced in the output image.

Additionally, a signal input into the reception unit 32 irrespectivelyof the image reading cycle is anticipated to be a signal withsuperimposed noise. Consequently, by setting a mask period in accordancewith a predetermined cycle (image reading cycle), the reception unit 32avoids receiving such signals with superimposed noise. As a result,compared to the case of not setting a mask period, the occurrence ofimage misalignment and misregistration caused by noise is reduced.

Note that in the second exemplary embodiment, a synchronization signalmay also be made up of a 1-bit signal, and the input or non-input of asynchronization signal may be recognized by “H” or “L” level.

Also, the first and second exemplary embodiments may be combined. Inthis case, a synchronization signal is made up of a 4-bit signal (signalpattern) similarly to the first exemplary embodiment, and the noisecancellation circuit 24A includes the recognition unit 34. For example,in the case in which a synchronization signal received by the receptionunit 32 is recognized as a genuine synchronization signal by therecognition unit 34, a mask period is set by treating as the start pointthe time of the reception of that synchronization signal. In so doing,the incorrect setting of a mask period in accordance with asynchronization signal with superimposed noise is avoided, and comparedto the case of not recognizing whether a synchronization signal isgenuine or non-genuine, the mask period is set more accurately. As aresult, the occurrence of image misalignment and misregistration isreduced.

The above example deals with a color image, but may also deal with amonochrome image. Even in this case, compared to the case of not settinga mask period, the occurrence of image misalignment caused by noise isreduced in the output image.

Note that although a line-sequential method is used in the aboveexample, a point-sequential method may also be used. Even in this case,by setting a mask period, in the case in which a color image isgenerated, the occurrence of image misalignment and misregistration isreduced compared to the case of not setting a mask period, while in thecase in which a monochrome image is generated, the occurrence of imagemisalignment is reduced compared to the case of not setting a maskperiod.

Third Exemplary Embodiment

Hereinafter, an image processing system according to the third exemplaryembodiment will be described with reference to FIGS. 6 and 7. FIG. 7 isa block diagram illustrating a noise cancellation circuit 24B accordingto the third exemplary embodiment.

The image processing system according to the third exemplary embodimentincludes the noise cancellation circuit 24B illustrated in FIG. 7instead of the noise cancellation circuit 24 according to the firstexemplary embodiment. The configuration other than the noisecancellation circuit 24B is the same as the configuration according tothe first exemplary embodiment. Hereinafter, the noise cancellationcircuit 24B will be described.

The noise cancellation circuit 24B includes a reception unit 32, asynchronization signal generation unit 40, and an output unit 36. Sincethe reception unit 32 and the output unit 36 are provided with the samefunctions as in the first exemplary embodiment, description thereof willbe reduced or omitted.

The synchronization signal generation unit 40 is provided with afunction in which, after the reception unit 32 receives asynchronization signal, in the case in which the next synchronizationsignal is not received within a predetermined reception period, thesynchronization signal generation unit 40 generates the nextsynchronization signal after the reception period elapses. The receptionunit 32 receives the next synchronization signal generated by thesynchronization signal generation unit 40. With this configuration, thereception unit 32 conducts an automatic reception process.

As described above, since the sensor 16 conducts image reading in apredetermined color order every one CLK in accordance with apredetermined image reading cycle, the timing at which the input imagesignal and the synchronization signal for each color are received by thereception unit 32 is predicted. After the reception unit 32 receives asynchronization signal, the synchronization signal generation unit 40sets a reception period by treating the timing at which the receptionunit 32 is predicted to receive the next synchronization signal as astart point, and in the case in which the reception unit 32 does notreceive the next synchronization signal within the reception period, thesynchronization signal generation unit 40 generates the nextsynchronization signal after the reception period elapses. The end pointof the reception period is set to a time before the timing at which thereception unit 32 is predicted to receive the subsequent synchronizationsignal after the next (that is, the synchronization signal after thenext synchronization signal). In other words, the reception period isset spanning from the time at which the reception unit 32 is predictedto receive the next synchronization signal until a time before the timeat which the reception unit 32 is predicted to receive the subsequentsynchronization signal after the next.

Hereinafter, processing by the synchronization signal generation unit 40will be described with reference to FIG. 6. Note that in the thirdexemplary embodiment, a mask period is not set.

For example, in the case in which the reception unit 32 receives thesynchronization signal 42G1, the timing (time 56) at which the receptionunit 32 is to receive the next synchronization signal, namely thesynchronization signal 42B1, is predicted, and a reception period 58 isset by treating that time 56 as the start point. The reception period 58is set spanning from the time 56 at which the reception unit 32 ispredicted to receive the next synchronization signal, namely thesynchronization signal 42B1 (start point) until a time 60 before thetime at which the reception unit 32 is predicted to receive thesynchronization signal after the next, namely the synchronization signal42R2 (end point). In the example illustrated in FIG. 6, the nextsynchronization signal, namely the synchronization signal 42B1, is notreceived by the reception unit 32 within the reception period 58. Inthis case, the synchronization signal generation unit 40 generates asynchronization signal 46B1 corresponding to the synchronization signal42B1. For example, in the case in which the synchronization signal 42B1is not received by the reception unit 32 due to noise, thesynchronization signal 46B1 corresponding to the synchronization signal42B1 is generated automatically.

Note that the length of the reception period may be shorter than thelength of the reception period described above. For example, in the casein which the reception unit 32 does not receive the next synchronizationsignal 42B1 by the time 56 at which the reception unit 32 is predictedto receive the next synchronization signal 42B1, the synchronizationsignal generation unit 40 may generate the synchronization signal 46B1corresponding to the synchronization signal 42B1.

The output unit 36 outputs the output data 50R1, 50G1, and so on, thesynchronization signals 52R1, 52G1, and so on, and the synchronizationsignals 54R1, 54R2, and so on to the image writing circuit 26downstream.

The synchronization signal 52B1 (output RLSO_RGB) in FIG. 6 is a signalcorresponding to the automatically generated synchronization signal 46B1(s_lso). In the case in which a synchronization signal is generatedautomatically, the reception unit 32 receives the automaticallygenerated synchronization signal after a delay equal to the length ofthe reception period 58. The output unit 36 holds the input image signal(for example, the input data 40B1) for the duration of the receptionperiod 58, and in accordance with the timing of the automatic receptionby the reception unit 32, outputs the held input image signal (theoutput data 50B1 which is the same as the input data 40B1) to the imagewriting circuit 26 downstream. With this arrangement, the occurrence ofdesynchronization of the input image signal (the output data 50B1)corresponding to the automatically generated synchronization signal(desynchronization with the input image signals on the same line, namelythe output data 50R1 and 50G1) is avoided.

According to the third exemplary embodiment, in the case in which asynchronization signal is not received by the reception unit 32 withinthe reception period, a synchronization signal is generatedautomatically. With this arrangement, in the case in which asynchronization signal is not received by the reception unit 32 within apredetermined period, the occurrence of image misalignment andmisregistration is reduced compared to the case of not conducting theprocessing when a synchronization signal is received until the receptionunit 32 receives the next synchronization signal.

In the case in which a synchronization signal is not received by thereception unit 32 and a synchronization signal is not generatedautomatically, the next synchronization signal after thatsynchronization signal is recognized as that synchronization signal, andas a result, image misalignment and misregistration occurs. This pointwill be described in detail by citing a specific example. In the exampleillustrated in FIG. 6, in the hypothetical case that the synchronizationsignal 46B1 is not generated automatically, the next synchronizationsignal 42R2 (the synchronization signal for R on the second line) isrecognized as the synchronization signal 42B1 for B on the first line,and the input data 40R2 is recognized as the B-line input image signalfor the first line. As a result, image misalignment and misregistrationoccurs. In contrast, according to the third exemplary embodiment, sincethe synchronization signal 46B1 is generated automatically, the nextsynchronization signal 42R2 is kept from being misrecognized as thesynchronization signal 46B1, and as a result, the occurrence of imagemisalignment and misregistration is reduced compared to the case of notautomatically generating a synchronization signal. Note that in the casein which the input data 40B1 is not received by the reception unit 32for the first line, an output image signal is generated by the inputdata 40R1 and 40G1, but for the second and subsequent lines, an outputimage signal is generated by the R, G, B input data while also reducingthe occurrence of image misalignment and misregistration.

Note that in the third exemplary embodiment, a synchronization signalmay also be made up of a 1-bit signal, and the input or non-input of asynchronization signal may be recognized by “H” or “L” level.

Also, the first and third exemplary embodiments may be combined. In thiscase, a synchronization signal is made up of a 4-bit signal (signalpattern) similarly to the first exemplary embodiment, and the noisecancellation circuit 24B includes the recognition unit 34. For example,in the case in which a synchronization signal received by the receptionunit 32 within the reception period is not recognized as a genuinesynchronization signal by the recognition unit 34, the synchronizationsignal generation unit 40 automatically generates a synchronizationsignal corresponding to that synchronization signal. In so doing, asignal that is not a synchronization signal is kept from beingrecognized as a synchronization signal, and thus the occurrence of imagemisalignment and misregistration is reduced further compared to the caseof not recognizing whether a synchronization signal is genuine ornon-genuine. Obviously, the synchronization signal generation unit 40also generates a synchronization signal automatically in the case inwhich a synchronization signal is not received by the reception unit 32within the reception period. Also, in the case in which asynchronization signal received by the reception unit 32 within thereception period is recognized as a genuine synchronization signal bythe recognition unit 34, the synchronization signal generation unit 40does not generate a synchronization signal.

The above example deals with a color image, but may also deal with amonochrome image. Even in this case, compared to the case of notautomatically generating a synchronization signal when a synchronizationsignal is not received by the reception unit 32, the occurrence of imagemisalignment caused by noise is reduced in the output image.

Note that although a line-sequential method is used in the aboveexample, a point-sequential method may also be used. Even in this case,by automatically generating a synchronization signal in the case inwhich a synchronization signal is not received by the reception unit 32,in the case in which a color image is generated, the occurrence of imagemisalignment and misregistration is reduced compared to the case of notautomatically generating a synchronization signal, while in the case inwhich a monochrome image is generated, the occurrence of imagemisalignment is reduced compared to the case of not automaticallygenerating a synchronization signal.

Fourth Exemplary Embodiment

Hereinafter, an image processing system according to the fourthexemplary embodiment will be described with reference to FIGS. 6 and 8.FIG. 8 is a block diagram illustrating a noise cancellation circuit 24Caccording to the fourth exemplary embodiment.

The image processing system according to the fourth exemplary embodimentincludes the noise cancellation circuit 24C illustrated in FIG. 8instead of the noise cancellation circuit 24 according to the firstexemplary embodiment. The configuration other than the noisecancellation circuit 24C is the same as the configuration according tothe first exemplary embodiment. Hereinafter, the noise cancellationcircuit 24C will be described.

The noise cancellation circuit 24C includes a reception unit 32, a masksetting unit 38, a synchronization signal generation unit 40, and anoutput unit 36. Since the reception unit 32 and the output unit 36 areprovided with the same functions as in the first exemplary embodiment,description thereof will be reduced or omitted.

Hereinafter, processing by the noise cancellation circuit 24C accordingto the fourth exemplary embodiment will be described with reference toFIG. 6.

Similarly to the second exemplary embodiment, after the reception unit32 receives a synchronization signal, the mask setting unit 38 sets amask period by treating the time of the reception as the start point.With this arrangement, the reception unit 32 does not receive asynchronization signal during the mask period, and instead receives asynchronization signal during the time after the mask period elapses butbefore the next mask period is set. For example, in the case in whichthe synchronization signal 42R1 is received by the reception unit 32, amask period 44R1 is set in response to the reception, and during thismask period, the reception unit 32 does not receive a synchronizationsignal. Similarly to the second exemplary embodiment, the reception unit32 receives input data (an input image signal) even during the maskperiod. After the mask period 44R1 elapses, when the synchronizationsignal 42G1 is input into the reception unit 32, the reception unit 32receives the synchronization signal 42G1. After this reception, a maskperiod 44G1 is set. Thereafter, the process is similar.

Similarly to the third exemplary embodiment, after the reception unit 32receives a synchronization signal, in the case in which the nextsynchronization signal is not received within a reception period, thesynchronization signal generation unit 40 generates the nextsynchronization signal after the reception period elapses. For example,in the case in which the reception unit 32 does not receive thesynchronization signal 42B1 within the reception period 58, after thereception period 58 elapses, the synchronization signal generation unit40 generates the synchronization signal 46B1 corresponding to thesynchronization signal 42B1. The reception unit 32 receives thesynchronization signal 46B1.

In the case in which a synchronization signal is generated by thesynchronization signal generation unit 40, the mask setting unit 38 setsa mask period by treating as the start point the time at which thereception unit 32 receives the generated synchronization signal. In thiscase, the mask setting unit 38 shortens the mask period by the length ofthe reception period 58. In the example illustrated in FIG. 6, a maskperiod 44B1 is set after the automatically generated synchronizationsignal 46B1, and the length of the mask period 44B1 is shortened by thelength of the reception period 58. In the case in which asynchronization signal is generated by the synchronization signalgeneration unit 40, the reception unit 32 receives the automaticallygenerated synchronization signal after a delay equal to the length ofthe reception period 58. In this case, the cycle of reception of asynchronization signal by the reception unit 32 is shifted from originalcycle (a cycle corresponding to the cycle of imaging reading by thesensor 16), but by shortening the length of the mask period 44B1 by thelength of the reception period 58 as above, the shifted cycle returns tothe original cycle.

According to the fourth exemplary embodiment, since a synchronizationsignal is not received during the mask period, a synchronization signalwith superimposed noise, for example, is kept from being received by thereception unit 32. With this arrangement, compared to the case of notsetting a mask period, the occurrence of image misalignment andmisregistration caused by noise is reduced in the output image. Also,since a synchronization signal is generated automatically in the case inwhich a synchronization signal is not received by the reception unit 32within the reception period, the occurrence of image misalignment andmisregistration is reduced compared to the case of not conducting theprocessing when a synchronization signal is received until the receptionunit 32 receives the next synchronization signal. By combining thesetting of a mask period with the automatic generation of asynchronization signal, the effects provided by both configurations areobtained, thereby further reducing image misalignment andmisregistration.

Note that in the fourth exemplary embodiment, a synchronization signalmay also be made up of a 1-bit signal, and the input or non-input of asynchronization signal may be recognized by “H” or “L” level.

Also, the first and fourth exemplary embodiments may be combined. Inthis case, a synchronization signal is made up of a 4-bit signal (signalpattern) similarly to the first exemplary embodiment, and the noisecancellation circuit 24C includes the recognition unit 34. For example,in the case in which a synchronization signal received by the receptionunit 32 is recognized as a genuine synchronization signal by therecognition unit 34, a mask period is set by treating as the start pointthe time of the reception of that synchronization signal. In so doing,the incorrect setting of a mask period in accordance with asynchronization signal with superimposed noise is avoided, and comparedto the case of not recognizing whether a synchronization signal isgenuine or non-genuine, the mask period is set more accurately. Also, inthe case in which a synchronization signal received by the receptionunit 32 within the reception period is not recognized as a genuinesynchronization signal by the recognition unit 34, the synchronizationsignal generation unit 40 automatically generates a synchronizationsignal corresponding to that synchronization signal. In so doing, asignal that is not a synchronization signal is kept from beingrecognized as a synchronization signal, and thus the occurrence of imagemisalignment and misregistration is reduced further compared to the caseof not recognizing whether a synchronization signal is genuine ornon-genuine. Obviously, the synchronization signal generation unit 40also generates a synchronization signal automatically in the case inwhich a synchronization signal is not received by the reception unit 32within the reception period.

The above example deals with a color image, but may also deal with amonochrome image. Also, as a method other than the line-sequentialmethod, a point-sequential method may also be used.

Fifth Exemplary Embodiment

Hereinafter, an image processing system according to the fifth exemplaryembodiment will be described with reference to FIGS. 8 and 9. FIG. 9 isa diagram illustrating a timing chart.

The image processing system according to the fifth exemplary embodimentincludes the same configuration as the image processing system accordingto the fourth exemplary embodiment. In the image processing systemaccording to the fifth exemplary embodiment, the noise cancellationcircuit 24C illustrated in FIG. 8 is used.

In the fifth exemplary embodiment, in the case in which the receptionunit 32 receives an initial synchronization signal for a unit of imagereading, the synchronization signal generation unit 40 automaticallygenerates the subsequent synchronization signals, and the reception unit32 receives the synchronization signals generated by the synchronizationsignal generation unit 40. Described more specifically, in the case inwhich the reception unit 32 receives the synchronization signal of theleading line (the first line) of a page targeted for image reading asthe initial synchronization signal, the synchronization signalgeneration unit 40 automatically generates the subsequentsynchronization signals, and the reception unit 32 receives thesynchronization signals generated by the synchronization signalgeneration unit 40.

Hereinafter, processing by the noise cancellation circuit 24C accordingto the fifth exemplary embodiment will be described with reference toFIG. 9.

As illustrated in FIG. 9, when the reception unit 32 receives theinitial synchronization signal, namely the synchronization signal 42R1,the mask setting unit 38 sets the mask period 44R1 after the receptionof the synchronization signal 42R1. In the fifth exemplary embodiment,the length of the mask period 44R1 is equal to the length of one CLK.With this arrangement, since the mask period 44R1 is set to include thetime 62 at which the reception unit 32 is predicted to receive the nextsynchronization signal, namely the synchronization signal 42G1, even ifthe next synchronization signal, namely the synchronization signal 42G1,is input into the reception unit 32 correctly in accordance with theimage reading cycle, the reception unit 32 does not receive thesynchronization signal 42G1. After the time 62 elapses, thesynchronization signal generation unit 40 automatically generates asynchronization signal 46G1 corresponding to the synchronization signal42G1. After the mask period 44R1, the mask setting unit 38 sets a maskperiod 44G1 corresponding to the next synchronization signal 42G1. Thelength of this mask period 44G1 is also equal to the length of one CLK,similarly to the mask period 44R1. With this arrangement, the receptionunit 32 does not receive the next synchronization signal, namely thesynchronization signal 42B1, and the synchronization signal generationunit 40 automatically generates a synchronization signal 46B1corresponding to the synchronization signal 42B1.

Thereafter, the process is similar. In other words, when the initialsynchronization signal 42R1 is received by the reception unit 32,thereafter mask periods are set, and the reception unit 32 does notreceive the synchronization signals sent after the synchronizationsignal 42R1. In this case, the synchronization signal generation unit 40automatically generates synchronization signals corresponding to thesynchronization signals sent after the synchronization signal 42R1, andthe reception unit 32 receives the automatically generatedsynchronization signals.

The initial synchronization signal 42R1 corresponds to thesynchronization signal of the leading line of a page targeted for imagereading, and in the case in which the reception unit 32 receives thesynchronization signal of the leading line of the page, thesynchronization signal generation unit 40 generates the subsequentsynchronization signals.

According to the fifth exemplary embodiment, after the initialsynchronization signal 42R1 is received by the reception unit 32, thereception unit 32 receives input data (input image signals) as thoughsynchronization signals are being input into the reception unit 32 inaccordance with the predetermined image reading cycle. In so doing, evenif noise is superimposed onto the second and subsequent synchronizationsignals, the reception of input data (input image signals) and thewriting to the memory 28 are conducted without being affected by suchnoise. As a result, the occurrence of image misalignment andmisregistration is reduced compared to the case of conducting processingonly in the case in which the reception unit 32 also receives asynchronization signal for the second and subsequent synchronizationsignals.

Note that in the example illustrated in FIG. 9, multiple mask periodshaving the same length (the length of one CLK) are set, but after thereception unit 32 receives the initial synchronization signal 42R1, asingle mask period that prohibits the reception of subsequentsynchronization signals by the reception unit 32 thereafter may also beset. Even in this case, when a synchronization signal is generated bythe synchronization signal generation unit 40, the reception unit 32receives the synchronization signal generated by the synchronizationsignal generation unit 40.

In the fifth exemplary embodiment, a synchronization signal may also bemade up of a 1-bit signal, and the input or non-input of asynchronization signal may be recognized by “H” or “L” level.

Also, the first and fifth exemplary embodiments may be combined. In thiscase, a synchronization signal is made up of a 4-bit signal (signalpattern) similarly to the first exemplary embodiment, and the noisecancellation circuit 24C includes the recognition unit 34. For example,in the case in which the initial synchronization signal 42R1 received bythe reception unit 32 is recognized as a genuine synchronization signalby the recognition unit 34, or in other words, in the case in which thesignal pattern included in the synchronization signal 42R1 matches thesignal pattern of the synchronization signal for R, thereafter, the masksetting unit 38 sets a mask period, the synchronization signalgeneration unit 40 automatically generates a synchronization signal, andthe reception unit 32 receives the synchronization signal generated bythe synchronization signal generation unit 40. By having the recognitionunit 34 recognize the synchronization signal, the synchronization signalof the leading line is identified more accurately compared to the caseof not conducting such recognition. With this arrangement, theoccurrence of image misalignment and misregistration is reduced furthercompared to the case of not recognizing the synchronization signal.

The above example deals with a color image, but may also deal with amonochrome image. Also, as a method other than the line-sequentialmethod, a point-sequential method may also be used.

Sixth Exemplary Embodiment

Hereinafter, an image processing system according to the sixth exemplaryembodiment will be described with reference to FIGS. 8 and 10. FIG. 10is a diagram illustrating a timing chart.

The image processing system according to the sixth exemplary embodimentincludes the same configuration as the image processing system accordingto the fourth exemplary embodiment. In the image processing systemaccording to the sixth exemplary embodiment, the noise cancellationcircuit 24C illustrated in FIG. 8 is used.

In the sixth exemplary embodiment, in the case in which the receptionunit 32 receives an initial synchronization signal for a unit of imagereading, the synchronization signal generation unit 40 automaticallygenerates the subsequent synchronization signals, and the reception unit32 receives the synchronization signals generated by the synchronizationsignal generation unit 40. Described more specifically, in the case inwhich the reception unit 32 receives the initial synchronization signal,namely the synchronization signal for R (corresponding to an example ofa synchronization signal for the first color) from among thesynchronization signal for R, the synchronization signal for G, and thesynchronization signal for B on the same line, the synchronizationsignal generation unit 40 automatically generates the synchronizationsignal for G and the synchronization signal for B in accordance with apredetermined image reading cycle (a cycle corresponding to the lengthof one CLK), and the reception unit 32 receives the synchronizationsignal for G and the synchronization signal for B generated by thesynchronization signal generation unit 40. Thereafter, the same processis repeated.

Hereinafter, processing by the noise cancellation circuit 24C accordingto the sixth exemplary embodiment will be described with reference toFIG. 10.

As illustrated in FIG. 10, when the reception unit 32 receives thesynchronization signal for the initial color (R) on the first (initial)line, namely the synchronization signal 42R1 (the synchronization signalof the first R-line), the mask setting unit 38 sets a mask period 44R1by treating as the start point the time of the reception of thesynchronization signal 42R1. In the sixth exemplary embodiment, the maskperiod 44R1 is set to include the time 62 at which the reception unit 32is predicted to receive the next synchronization signal on the firstline, namely the synchronization signal 42G1 (the synchronization signalof the first G-line). In the example illustrated in FIG. 10, the maskperiod 44R1 is set spanning from the time at which the reception unit 32receives the synchronization signal 42R1 until the time at which thereception unit 32 is predicted to complete reception of the nextsynchronization signal 42G1. With this arrangement, even if the nextsynchronization signal, namely the synchronization signal 42G1, is inputinto the reception unit 32 correctly in accordance with thepredetermined image reading cycle (a cycle corresponding to the lengthof one CLK), the reception unit 32 does not receive the synchronizationsignal 42G1. After the mask period 44R1 elapses, the synchronizationsignal generation unit 40 automatically generates a synchronizationsignal 46G1 corresponding to the synchronization signal 42G1. Thereception unit 32 receives the automatically generated synchronizationsignal 46G1.

Next, the mask setting unit 38 sets a mask period 44G1 corresponding tothe synchronization signal 42G1 on the first line by treating as thestart point the time at which the reception unit 32 receives thesynchronization signal 46G1. The mask period 44G1 is set to include atime 56 at which the reception unit 32 is predicted to receive the nextsynchronization signal on the first line, namely the synchronizationsignal 42B1 (the synchronization signal of the first B-line). In theexample illustrated in FIG. 10, the mask period 44G1 is set spanningfrom the time at which the reception unit 32 receives thesynchronization signal 46G1 until the time at which the reception unit32 is predicted to complete reception of the next synchronization signal42B1. With this arrangement, even if the next synchronization signal,namely the synchronization signal 42B1, is input into the reception unit32 correctly in accordance with the predetermined image reading cycle (acycle corresponding to the length of one CLK), the reception unit 32does not receive the synchronization signal 42B1. After the mask period44G1 elapses, the synchronization signal generation unit 40automatically generates a synchronization signal 46B1 corresponding tothe synchronization signal 42B1. The reception unit 32 receives theautomatically generated synchronization signal 46B1.

The mask period 44R1 corresponding to the synchronization signal for Ris set by treating as the start point the time at which the receptionunit 32 receives the synchronization signal 42R1, while the mask period44G1 corresponding to the synchronization signal for G is set bytreating as the start point the time at which the reception unit 32receives the automatically generated synchronization signal 46G1. Sincethe mask period 44G1 is set by treating as the start point the time atwhich the synchronization signal 46G1 is automatically generated andreceived by the reception unit 32, the mask period 44G1 is set bytreating as the start point a time after the time at which the receptionunit 32 is predicted to receive the original synchronization signal42G1. For this reason, the length of the mask period 44G1 is shorterthan the length of the mask period 44R1 set previously.

Next, the mask setting unit 38 sets a mask period 44B1 corresponding tothe synchronization signal 42B1 by treating as the start point the timeat which the reception unit 32 receives the synchronization signal 46B1.The mask period 44B1 is set not to include the time 60 at which thereception unit 32 is predicted to receive the synchronization signal forthe second (next) line, namely the synchronization signal 42R2. In theexample illustrated in FIG. 10, the mask period 44B1 is set spanningfrom the time at which the reception unit 32 receives thesynchronization signal 46B1 until a time before the time at which thereception unit 32 is predicted to receive the synchronization signal forthe second line, namely the synchronization signal 42R2 (thesynchronization signal of the second R-line). With this arrangement, inthe case in which the synchronization signal for the initial color (R)on the second line, namely the synchronization signal 42R2, is inputinto the reception unit 32 correctly in accordance with thepredetermined image reading cycle (a cycle corresponding to the lengthof one CLK), the synchronization signal 42R2 is received by thereception unit 32. In this way, when the reception unit 32 receives thesynchronization signal 42R2 for the second line, similarly to the firstline, mask periods 44R2, 44G2, and 44B2 are set, and a synchronizationsignal 46G2 for G and a synchronization signal 46B2 for B are generatedautomatically. The reception unit 32 receives the automaticallygenerated synchronization signals 46G2 and 46B2. The subsequent linesare also similar.

As above, in the sixth exemplary embodiment, the reception of asynchronization signal for R, and the automatic generation and receptionof a synchronization signal for G and a synchronization signal for B,are executed in units of lines. In the case in which a synchronizationsignal for the initial color (R) for each line is received by thereception unit 32, the reception unit 32 receives input data (inputimage signals) as though synchronization signals for the other colors(G, B) are being input in accordance with the predetermined cycle. In sodoing, even noise is superimposed onto the synchronization signals fortwo out of three colors (namely, the second color and the third color),the reception of input data (input image signals) and the writing to thememory 28 are conducted without being affected by such noise. As aresult, the occurrence of image misalignment and misregistration isreduced compared to the case of conducting processing only in the casein which the reception unit 32 also receives synchronization signals forthe second color and the third color. Also, by processing in units oflines, incorrect operation caused by the noise or the like is concludedon a single line, while the images of other lines remain unaffected.

Also, in the sixth exemplary embodiment, on each line, mask periodshaving a different length for each color are set. Specifically, from theinitial color (R) to the second color (G) and the third color (B),respective mask periods are set in which the length gradually becomesshorter. By setting mask periods in this way, the synchronizationsignals for the second color (G) and the third color (B) are kept frombeing received by the reception unit 32, and in addition, the initialcolor (R) for the second and subsequent lines is received by thereception unit 32. With this arrangement, the reception of asynchronization signal for R, and the automatic generation and receptionof a synchronization signal for G and a synchronization signal for B,are executed correctly in units of lines.

In the sixth exemplary embodiment, a synchronization signal may also bemade up of a 1-bit signal, and the input or non-input of asynchronization signal may be recognized by “H” or “L” level.

Also, the first and sixth exemplary embodiments may be combined. In thiscase, a synchronization signal is made up of a 4-bit signal (signalpattern) similarly to the first exemplary embodiment, and the noisecancellation circuit 24C includes the recognition unit 34. For example,in the case in which the synchronization signal 42R1 for the initialcolor (R) received by the reception unit 32 is recognized as a genuinesynchronization signal by the recognition unit 34, or in other words, inthe case in which the signal pattern included in the synchronizationsignal 42R1 matches the prescribed pattern of the synchronization signalfor R, the mask setting unit 38 sets the mask period 44R1, thesynchronization signal generation unit 40 generates the synchronizationsignal 46G1 for G, and the reception unit 32 receives thesynchronization signal 46G1. Thereafter, the process is similar.Likewise for the second and subsequent lines, in the case in which thesynchronization signal for the initial color (R) is recognized as agenuine synchronization signal, the setting of mask periods and theautomatic generation of synchronization signals are conducted. By havingthe recognition unit 34 recognize the synchronization signal, thesynchronization signal for the initial color on each line is identifiedmore accurately compared to the case of not conducting such recognition.With this arrangement, the occurrence of image misalignment andmisregistration is reduced compared to the case of not recognizing thesynchronization signal.

The above example deals with a color image, but may also deal with amonochrome image. Also, as a method other than the line-sequentialmethod, a point-sequential method may also be used.

Note that in the case in which a synchronization signal is generatedautomatically, the reception unit 32 receives the automaticallygenerated synchronization signal after a delay equal to the time takenby the automatic generation. In this case, the output unit 36 holds theinput data (input image signal) for the duration of the delay time, andin accordance with the timing of the automatic reception by thereception unit 32, outputs the held input data to the image writingcircuit 26 downstream. With this arrangement, the occurrence ofdesynchronization of an input image signal corresponding to anautomatically generated synchronization signal is avoided.

Seventh Exemplary Embodiment

Hereinafter, an image processing system according to the seventhexemplary embodiment will be described with reference to FIGS. 8 and 11.FIG. 11 is a diagram illustrating a timing chart.

The image processing system according to the seventh exemplaryembodiment includes the same configuration as the image processingsystem according to the fourth exemplary embodiment. In the imageprocessing system according to the seventh exemplary embodiment, thenoise cancellation circuit 24C illustrated in FIG. 8 is used.

Hereinafter, processing by the noise cancellation circuit 24C accordingto the seventh exemplary embodiment will be described with reference toFIG. 11.

In the seventh exemplary embodiment, a synchronization signal isgenerated only for a specific color, and not generated for colors otherthan the specific color. The specific color is R (red), for example, andin the AFE 18, only the synchronization signal for R is generated, whilethe synchronization signals for G and B are not generated. Asillustrated in FIG. 11, the synchronization signals 42R1, 42R2, and soon for R are input into the reception unit 32, and the reception unit 32receives the synchronization signals 42R1, 42R2, and so on for R. Whenthe reception unit 32 receives a synchronization signal for R, thesynchronization signal generation unit 40 automatically generates asynchronization signal for G and a synchronization signal for B inaccordance with a predetermined image reading cycle (a cyclecorresponding to the length of one CLK), and the reception unit 32receives the synchronization signal for G and the synchronization signalfor B generated by the synchronization signal generation unit 40.Thereafter, the same process is repeated.

Note that the mask setting unit 38 may also set a mask period other thanin a period in which the reception unit 32 is predicted to receive thesynchronization signal for R, in accordance with a predetermined imagereading cycle (a cycle corresponding to the length of one CLK). Withthis arrangement, a signal that is not a synchronization signal is keptfrom being received by the reception unit 32 as a synchronizationsignal, and thus the occurrence of image misalignment andmisregistration is reduced compared to the case of not setting a maskperiod.

The mask setting unit 38 sets a mask period until before the time atwhich the reception unit 32 is predicted to receive the nextsynchronization signal for R, and in the case in which the receptionunit 32 receives the next synchronization signal for R, the next maskperiod may be set by treating as the start point the time at which thereception unit 32 receives the synchronization signal for R. By settinga mask period in this way, for example, even if a mask period would beset incorrectly to a period in which the reception unit 32 is predictedto receive a synchronization signal for R as a result of noise beingsuperimposed onto the base clock signal (CLK), a mask period is not setuntil the reception unit 32 receives the next synchronization signal forR, and that next synchronization signal for R is received by thereception unit 32. With this arrangement, even if a discrepancy isproduced between the mask period and the reception period of asynchronization signal by the reception unit 32, when a latersynchronization signal for R is received by the reception unit 32, thediscrepancy between the mask period and the reception period isaddressed at that time, and the mask period and the reception period aresynchronized correctly.

Note that a mask period may also not be set. In this case, the masksetting unit 38 is not included in the noise cancellation circuit 24C.

As above, according to the seventh exemplary embodiment, in the case inwhich a synchronization signal for a specific color (R) for each line isreceived by the reception unit 32, the reception unit 32 receives inputdata (input image signals) as though synchronization signals for theother colors (G, B) are being input in accordance with the predeterminedcycle. In so doing, the occurrence of image misalignment andmisregistration is reduced compared to the case of also generatingsynchronization signals for the second and third colors, and conductingprocessing only in the case in which the reception unit 32 also receivesthose synchronization signals.

In the seventh exemplary embodiment, a synchronization signal may alsobe made up of a 1-bit signal, and the input or non-input of asynchronization signal may be recognized by “H” or “L” level.

Also, the first and seventh exemplary embodiments may be combined. Inthis case, a synchronization signal is made up of a 4-bit signal (signalpattern) similarly to the first exemplary embodiment, and the noisecancellation circuit 24C includes the recognition unit 34. For example,in the case in which the synchronization signal 42R1 received by thereception unit 32 is recognized as a genuine synchronization signal (asynchronization signal for a specific color) by the recognition unit 34,or in other words, in the case in which the signal pattern included inthe synchronization signal 42R1 matches the prescribed pattern of thesynchronization signal for R, the synchronization signal generation unit40 generates the synchronization signal 46G1 for G and thesynchronization signal 46B1 for B. Thereafter, the process is similar.Likewise for the second and subsequent lines, in the case in which thesynchronization signal for the specific color (R) is recognized as agenuine synchronization signal, the automatic generation ofsynchronization signals is conducted. Also, in the case in which asynchronization signal received by the reception unit 32 is recognizedas a genuine synchronization signal, the mask setting unit 38 may alsoset a mask period. By having the recognition unit 34 recognize thesynchronization signal, the synchronization signal for the specificcolor is identified more accurately compared to the case of notconducting such recognition. With this arrangement, the occurrence ofimage misalignment and misregistration is reduced compared to the caseof not recognizing the synchronization signal.

The above example deals with a color image, but may also deal with amonochrome image. Also, as a method other than the line-sequentialmethod, a point-sequential method may also be used.

The above image processing circuit 20 is realized by the cooperativeaction of hardware and software as an example. Specifically, the imageprocessing circuit 20 is provided with one or multiple processors suchas CPUs (not illustrated). By having the one or multiple processors loadand execute a program stored in a storage device (not illustrated), thefunctions of the respective units of the image processing circuit 20 arerealized. The program is stored in the storage device via a recordingmedium such as a CD or DVD, or alternatively, via a communication linksuch as a network. As another example, the respective units of the imageprocessing circuit 20 may be realized by hardware resources such as aprocessor, an electronic circuit, an application-specific integratedcircuit (ASIC), or a system on a chip (SOC), for example. A device suchas memory may also be used in such a realization. As yet anotherexample, the respective units of the image processing circuit 20 mayalso be realized by a digital signal processor (DSP), afield-programmable gate array (FPGA), or the like.

The foregoing description of the exemplary embodiments of the presentinvention has been provided for the purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise forms disclosed. Obviously, many modificationsand variations will be apparent to practitioners skilled in the art. Theembodiments were chosen and described in order to best explain theprinciples of the invention and its practical applications, therebyenabling others skilled in the art to understand the invention forvarious embodiments and with the various modifications as are suited tothe particular use contemplated. It is intended that the scope of theinvention be defined by the following claims and their equivalents.

What is claimed is:
 1. An image processing system comprising: an imagereading device that reads a physical image to generate an input imagesignal and to output the input image signal and a synchronizationsignal; at least one processor programmed to function as: a receptionunit that receives the input image signal and the synchronizationsignal, the synchronization signal used to generate an output imagesignal on a basis of the input image signal; and a setting unit thatsets, after the reception unit receives the synchronization signal, areception prohibition period that prohibits reception of a differentsynchronization signal by the reception unit, the reception prohibitionperiod being a mask period that is set for each of a plurality of colorsafter the reception unit receives the synchronization signal, whereinthe output image signal is a signal generated on a basis of input imagesignals for the plurality of colors, the reception unit receives theinput image signal expressing a respective color from among theplurality of colors, and the synchronization signal for each color, thesynchronization signal is a signal used to generate the output imagesignal by combining the input image signals for each of the colors, andthe setting unit sets the reception prohibition period for each color.2. The image processing system according to claim 1, wherein the atleast one processor is further programmed to function as: a generationunit that generates a synchronization signal, wherein the output imagesignal is a signal generated on a basis of input image signals for aplurality of colors, the reception unit receives the input image signalexpressing a respective color from among the plurality of colors, andthe synchronization signal for each color, the synchronization signal isa signal used to generate the output image signal by combining the inputimage signals for each of the colors, and in a case in which asynchronization signal for a first color among the plurality of colorsis received as an initial synchronization signal of a unit of imagereading, the generation unit generates a synchronization signal for eachcolor other than the first color among the plurality of colors, thesetting unit sets, after the reception unit receives the synchronizationsignal for the first color, the reception prohibition period thatprohibits reception, by the reception unit, of the synchronizationsignal for each color other than the first color, and the reception unitreceives each synchronization signal generated by the generation unit.3. The image processing system according to claim 1, wherein the atleast one processor is further programmed to function as: a generationunit that generates, in a case in which a synchronization signal for afirst color among the plurality of colors is received as an initialsynchronization signal of a unit of image reading, a synchronizationsignal for each color other than the first color among the plurality ofcolors, wherein the setting unit sets, after the reception unit receivesthe synchronization signal for the first color, the receptionprohibition period that prohibits reception, by the reception unit, ofthe synchronization signal for each color other than the first color,and the reception unit receives each synchronization signal generated bythe generation unit.
 4. The image processing system according to claim3, wherein the setting unit sets the reception prohibition period with adifferent length for each color.
 5. The image processing systemaccording to claim 4, wherein the setting unit shortens the length ofthe reception prohibition period set after the generation of thesynchronization signal for each color other than the first color to lessthan the length of the reception prohibition period set after thereception of the synchronization signal for the first color.
 6. Theimage processing system according to claim 1, wherein the receptionprohibition period is determined on a basis of a time at which thereception unit is predicted to receive the next input image signal. 7.The image processing system according to claim 6, wherein the receptionprohibition period is set spanning until a time before the time at whichthe reception unit is predicted to receive the next input image signal.8. The image processing system according to claim 1, wherein the inputimage signal is a signal generated by conducting image reading in unitsof lines, and the length of the reception prohibition period isdetermined on a basis of an image reading time for one line.
 9. Theimage processing system according to claim 8, wherein the length of thereception prohibition period is less than the length of the imagereading time for one line.
 10. The image processing system according toclaim 1, wherein in a case in which the reception unit does not receivethe next synchronization signal after the reception prohibition period,the reception unit conducts an automatic reception process that treatsthe next synchronization signal as being received.
 11. The imageprocessing system according to claim 10, wherein the at least oneprocessor is further programmed to function as: a generation unit thatgenerates the next synchronization signal in a case in which thereception unit does not receive the next synchronization signal afterthe reception prohibition period, wherein the reception unit receivesthe next synchronization signal generated by the generation unit as theautomatic reception process.
 12. The image processing system accordingto claim 1, wherein the synchronization signal is a signal including asignal pattern, and a genuine synchronization signal to be used togenerate the output image signal on a basis of the input image signal isidentified on a basis of the signal pattern.
 13. The image processingsystem according to claim 12, wherein the synchronization signal isidentified as a genuine synchronization signal in a case in which thesignal pattern corresponds to a predetermined prescribed pattern, andthe setting unit sets the reception prohibition period after thereception unit receives the identified synchronization signal.
 14. Theimage processing system according to claim 13, wherein the at least oneprocessor is further programmed to function as: a generation unit thatgenerates a synchronization signal corresponding to the synchronizationsignal in a case in which the signal pattern does not correspond to apredetermined prescribed pattern, wherein the reception unit receivesthe synchronization signal generated by the generation unit, and thesetting unit sets the reception prohibition period after thesynchronization signal is generated by the generation unit.
 15. Theimage processing system according to claim 1, wherein the receptionprohibition period is set to have a fixed length every one base clocksignal.
 16. A non-transitory computer readable medium storing a programcausing a computer to execute a process for processing an image, theprocess comprising: receiving an input image signal and asynchronization signal from an image reading device that generates thesynchronization signal and reads a physical image to generate the inputimage signal, the synchronization signal used to generate an outputimage signal on a basis of the input image signal; and setting, afterreceiving the synchronization signal, a reception prohibition periodthat prohibits reception of a different synchronization signal, thereception prohibition period being a mask period that is set for each ofa plurality of colors after the synchronization signal is received,wherein the output image signal is generated on a basis of receivedinput image signals for the plurality of colors, the received inputimage signal expresses a respective color from among the plurality ofcolors, and the synchronization signal for each color, thesynchronization signal is used to generate the output image signal bycombining the input image signals for each of the colors, and thereception prohibition period is set for each color.